I found an interesting issue with wasm on 2.0.20 ...

# webassembly

[Dmitriy Tarasevich]

I found an interesting issue with wasm on 2.0.20

Lets say I have the following code

sealed class FooBar {
    object Foo : FooBar()
    object Bar : FooBar()
}

fun takeFooBar(fooBar: FooBar) {
    // TBD
}

fun main() {
    // Wasm thinks this is an Any
    val bar = if (true) {
        FooBar.Foo
    } else {
        FooBar.Bar
    }
    takeFooBar(fooBar = bar)
}

ill get an error at runtime like the following

Uncaught (in promise) CompileError: WebAssembly.instantiateStreaming(): Compiling function #144978:"com.package..main..etc..." failed: call[2] expected type (ref null 37332), found local.get of type (ref null 2550) @[phone]

doing a wasm-objdump i can see that type 2550 is of type Any and 37332 is type FooBar

I have two ways of making this work by changing the code to either

val bar: FooBar = if (true) {
        FooBar.Foo
    } else {
        FooBar.Bar
    }

or

making the FooBar instances a class

sealed class FooBar {
    class Foo : FooBar()
    class Bar : FooBar()
}

fun takeFooBar(fooBar: FooBar) {
    // TBD
}

fun main() {
    // This works.
    val bar = if (true) {
        FooBar.Foo()
    } else {
        FooBar.Bar()
    }
    takeFooBar(fooBar = bar)
}

Is this a known issue? is there any work arounds as we use objects a lot in our code base and going through and adding types would be quite a chore.

[Artem Kobzar]

mmm, interesting. Could you please create a ticket for it?

[Dmitriy Tarasevich]

Yah for sure, ill get a sample project up showcasing this too

[Artem Kobzar]

May I also ask you check it with 2.1.0?

[Dmitriy Tarasevich]

that was my next step

[Dmitriy Tarasevich]

ill report back

[Artem Kobzar]

gratitude thank you

[Dmitriy Tarasevich]

in worse news.... 2.1 fails on our project with the following

kotlin.UninitializedPropertyAccessException: lateinit property body has not been initialized
	at org.jetbrains.kotlin.ir.declarations.impl.IrAnonymousInitializerImpl.getBody(IrAnonymousInitializerImpl.kt:37)

ill test it out on a sample i suppose. Any ideas on this error?

[Artem Kobzar]

It's an internal compiler error, so, need to debug and investigate the issue on a sample project

[Dmitriy Tarasevich]

Could this be because serialization is not yet pointing to 2.1?

[Artem Kobzar]

Maybe, because I can't reproduce it on the playground: https://pl.kotl.in/QXZuVLM1n

[Dmitriy Tarasevich]

Alright, I'll wait for them to publish a new version, hopefully not too long. 🤞